ampacity

Definitions

from Wiktionary, Creative Commons Attribution/Share-Alike License

n. The root mean square of the electrical current which a device (usually a wire) can carry within a specific environment (including temperature rating, power loss, heat dissipation, etc.) It is measured in amperes, (amps) and is most often used to rate electrical wires and cables.

Etymologies

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Examples

Figure 3 illustrates a 2,500 A breaker frame with a 1,600 A trip unit (higher ampacity trip units are available to the full-frame rating).

The number and size of loads in an industrial control panel or NEC installation frequently require a circuit breaker 800 A or greater to be used as a main device, with lower-ampacity circuits tapped from it.

In brief, the rules for tapping feeder circuits indicate that a conductor rated 10% of the ampacity of a feeder conductor may be tapped from the feeder, provided it is not greater than 10 ft in length and it terminates in an appropriately sized OCPD.